Making the player walk on walls in box2d

Question

I'm making a game in stencil where players walk form left to right along randomly generated walls. I cant use waypoints, since the walls' shapes and positions are unpredictable.

Here's a descriptive sketch:

The red line is the player's path. The red circles are what I thought might make good waypoints until I scrapped the idea.

Answer 1

Depending on what you actually wish to do , either 1) Change the gravitation upon colision with a wall, so it faces "into" the wall.

2) Add high friction for walls, equal 1 to the body fixture. It allows sticking to walls.

Answer 2

You can make a raycast from your character into all all four directions. If you only hit the ground then you don't have to do anything. If you hit a wall or the ceiling you add a weld joint to your character and the wall. You destroy and recreate the joint inside your update loop, so the character can move, but is tied to the wall/ceiling and doesn't fall down. There are still two tricky parts left.

1. Corners: When you come to a corner (two ray casts hit a wall) you must switch the wall on which you create the joint, depending on the direction you are walking to.
2. Walking direction: When you walk around a corner, you must track the direction you are walking to, so you can press forward all the time and follow the shape of the wall.